This invention relates to an apparatus for detecting a missing portion of an opaque body or a opaque body greater than a predetermined size and which is capable of detecting a pattern in a minute region.
A detecting apparatus of this type is used, for example, for quality control of a sheet of laver by detecting holes and chinks in such a sheet. Heretofore, such a detector has been provided as a system which has an image sensor light receiver comprising a large number of photodiodes for receiving light that is emitted from a light projector to illuminate a body to be detected and to detect defects in it. Unfortunately, the image sensor portion for detecting light is small and, therefore, light is required to be converged prior to illumination on the body. Further, as light is converged, accuracy in detection is severely affected by the performance of the optics used for convergence. Thus, expensive optics and image sensors are required to detect with high accuracy a body having holes and chinks of various size, position and shape, like a sheet of laver.